You can check if a PO file is valid with the following command:

        msgfmt -c -o /dev/null <po file>
      

The following errors were found in sumo 's PO files:

gettext: data/po/cs_sumo.po: can't guess language
gettext: data/po/de_sumo.po: can't guess language
gettext: data/po/es_sumo.po: can't guess language
gettext: data/po/fr_sumo.po: can't guess language
gettext: data/po/hu_sumo.po: can't guess language
gettext: data/po/it_sumo.po: can't guess language
gettext: data/po/ja_sumo.po: can't guess language
gettext: data/po/pt_sumo.po: can't guess language
gettext: data/po/ru_sumo.po: can't guess language
gettext: data/po/tr_sumo.po: can't guess language
gettext: data/po/uk_sumo.po: can't guess language
gettext: data/po/zh-Hant_py.po: py not a language code
gettext: data/po/zh-Hant_sumo.po: can't guess language
gettext: data/po/zh_sumo.po: can't guess language
      

Please ask the translator (identified by the Last-Translator field in the PO file), the language team (identified by the Language-Team field) or debian-i18n for a fix.